Investigation of the bipolar control strategy-based dynamic properties of a nonlinear bionic suspension system

Abstract

This paper presents a novel bionic X-shaped suspension designed to reduce vehicle body vibrations and enhance ride comfort. A dynamic model was developed to analyze its vibration characteristics. By adopting a bipolar control strategy that couples fuzzy logic with an incremental PID formulation, the incremental PID component provides a well-defined baseline regulation mechanism, thereby preserving closed-loop stability and satisfactory steady-state behavior. In parallel, the fuzzy logic module operates as an adaptive nonlinear gain scheduler that modulates the incremental PID channels according to the prevailing excitation conditions, enhancing robustness and dynamic responsiveness under varying road disturbances. This cooperative structure achieves rapid bipolar authority take-over with smooth and stable transitions, without introducing additional complexity to the underlying control law, thereby effectively overcoming the slow response and limited real-time performance of traditional controllers when applied to nonlinear structures. The system’s effectiveness was validated through numerical simulations and experiments under various road conditions. Under Grade C road conditions, the bipolar control strategy reduced the RMS vertical body acceleration by 87.50%, reduced the RMS values of both the suspension dynamic deflection and the tire dynamic load by 34.09% and 9.66%, respectively. In passive mode, the X-shaped suspension reduced the RMS vertical body acceleration by 47.54% and 54.29% compared to other bionic designs. Power spectral density (PSD) analysis indicates that within the human-sensitive frequency band (4–12 Hz), bipolar control provides the most consistent attenuation of the dominant spectral peaks in body acceleration, while also reducing the spectral levels of suspension dynamic deflection and tire dynamic load. Frequency response characteristics also confirmed that the suspension’s comfort and stability under bipolar control exceed those of alternative methods. A comparative study on suspension rod lengths indicated optimal vibration damping when the femur and tibia measured 0.4 m and the tarsus 0.2 m. Overall, the proposed bionic suspension structure and control strategy significantly mitigate vehicle vibrations and improve ride comfort, and these benefits are further corroborated through full-vehicle experimental validation, providing a solid basis for the further integration of nonlinear bionic structures with bipolar control in suspension systems.